JPH0437069B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a corresponding acrylamide or methacrylamide [hereinafter referred to as (meth)acrylamide] obtained by hydrating acrylonitrile or methacrylonitrile [hereinafter referred to as (meth)acrylonitrile]. ]Relating to a method for purifying an aqueous solution.
(Meth)acrylamide is extremely useful as a raw material for polymers that have many uses such as flocculants, thickeners, oil recovery agents, soil improvers, paper strength enhancers in the paper industry, sticky agents for papermaking, and water-based improvers. It is a substance.

Conventional technology Unsaturated amides such as acrylamide and methacrylamide are produced by contacting and hydrating the corresponding unsaturated nitrile with a metallic copper catalyst such as Raney copper, reduced copper, copper chromium, copper zinc, etc. in an aqueous medium. is widely known. Furthermore, recently, a method has been proposed for producing a corresponding unsaturated amide by hydrating an unsaturated nitrile using a microorganism capable of hydrating a nitrile.

Among these methods for producing unsaturated amides, especially when using a metallic copper catalyst, the reaction temperature is generally 60-60°C.
Because the temperature is 150℃ and the reaction pressure is as high as 0 to 20Kg/ ^cm2 , side reactions are likely to occur, and these byproducts (organic acids, etc.) and impurities such as metal ions derived from the catalyst are removed from the resulting amide aqueous solution. Purification operations are required. In particular, in order to use it as a raw material for the above-mentioned polymers, it is necessary to remove impurities that would adversely affect polymerization as much as possible.

When using microorganisms, the reaction is carried out at room temperature and pressure, so the amide aqueous solution produced contains less inorganic salts, reaction by-products, and eluates from microbial cells than when using metallic copper catalysts. Although there are very few impurities, it is preferable to remove these inorganic salts if the purpose is to produce a high-performance amide polymer.

Distillation, extraction, crystallization, etc. are conceivable methods for removing impurities from these amide aqueous solutions, but these methods require some form of heating operation, and are generally used for unsaturated amides that are unstable to heat. It is not suitable as a purification method.

As a method for removing impurities that has been put into practical use industrially, there is a method using an ion exchange resin. This method is effective in removing extremely small amounts of organic acids and inorganic salts, but when these impurities are on the order of a few percent of the unsaturated amide, a large amount of ion exchange resin is required. However, the regeneration frequency increases, the cost increases, and polymerization troubles are likely to occur near the resin.

Ion exchange resins can be broadly divided into cation exchange resins and anion exchange resins, and when containing impurities such as organic acids and inorganic salts as in the present invention, the above two types of resins are naturally required, and the resin The appropriate pH when a substance is adsorbed is naturally different for cationic resins and anionic resins, and therefore the degree of adsorption due to pH must also be considered. Furthermore, when handling unsaturated amides such as those used in the present invention, attention must be paid to polymerization troubles. That is, although the reason for the unsaturated amide aqueous solution is not well understood, polymerization occurs very often in the vicinity of the ion exchange resin when the pH is low (particularly when the pH is below 5).

Furthermore, as a method for removing unsaturated organic acids, a method has been proposed in which the aqueous solution is neutralized with an alkali and treated with a reverse osmosis membrane (Japanese Patent Application Laid-Open No. 1983-1999-
(Refer to Publication No. 92254). This method attempts to separate amide and water by passing them through a reverse osmosis membrane, but not allowing organic acids to pass through. However, in the case of similar molecular weights, for example, acrylamide and acrylic acid, In this case, the molecular weights are almost the same,
It is quite difficult to separate them cleanly.

Problems to be Solved by the Invention The present invention efficiently removes various impurities in the corresponding (meth)acrylamide aqueous solution obtained by hydrating (meth)acrylonitrile without causing troubles such as polymerization, and The aim is to obtain an aqueous (meth)acrylamide solution suitable as a raw material for combined production.

The impurities in the (meth)acrylamide aqueous solution that are to be removed in the present invention depend on the manufacturing conditions of (meth)acrylamide, but include organic acids, such as acrylic acid by-produced during acrylamide manufacturing, and the cultivation and immobilization of microorganisms. KCl derived from various additives used in preparation of bacterial cells, nitrile hydration reaction, etc.
NaCl, K ₂ SO ₄ , Na ₂ SO ₄ , K ₂ CO ₃ , Na ₂ CO ₃ ,
(NH ₄ ) ₂ CO ₃ , NH ₄ Cl, (CH ₄ ) ₂ SO ₄ , CaCl ₂ ,
CaSO ₄ , KNO ₃ , NaNO ₃ , NH ₄ NO ₃ , Ca
(NO ₃ ) ₂ , K ₃ PO ₄ , Na ₃ PO ₄ , K ₂ HPO ₄ ,
Na ₂ HPO ₄ , KH ₂ PO ₄ , NaH ₂ PO ₄ , K ₂ SiO ₃ ,
Na ₂ SiO ₃ , CaSiO ₃ , NH ₄ I, KI, NaI, Na ₃ BO ₃ ,
(NH ₄ ) ₂ CrO ₄ , K ₂ CrO ₄ , Na ₂ CrO ₄・₁₀ H ₂ O,
Inorganic salts such as (NH ₄ ) ₂ CO ₃ and (COONH ₄ ) ₂・H ₂ O,
(COOK) ₂・H ₂ O, C ₆ H ₅ CO ₂ Na・H ₂ O,
(C ₆ H ₅ CO ₂ ) ₂ Ca.3H ₂ O, C ₆ H ₅ SO ₃ Na, and other organic salts.

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present invention has revealed that the use of an ion exchange membrane is extremely effective for purifying (meth)acrylamide aqueous solutions containing various impurities. This is what was discovered.

That is, the present invention uses an anion exchange membrane as an anode of an electrodialysis device in which negative and positive electrodes are arranged at both ends of a plurality of liquid phase chambers partitioned by alternately arranged anion exchange membranes and cation exchange membranes. An aqueous solution of acrylamide or methacrylamide obtained by hydrating acrylonitrile or methacrylonitrile is placed in the liquid phase chamber on the facing side, and the ionic substances in the solution are permeated into the adjacent liquid phase chamber and removed. The gist of the present invention is a method for purifying an aqueous solution of acrylamide or methacrylamide.

According to the present invention, it is possible to efficiently remove (meth)acrylamide, which is electrically neutral at a certain pH range, and moreover, at a pH near neutrality, as well as organic acids, inorganic salts, organic salts, etc. that are electrolytes. is possible.

The difference between the method using the ion exchange membrane of the present invention and the method using ion exchange resins is that the PH
It is different from the reverse osmosis membrane method because the substance that passes through the membrane is an electrolyte, and it does not cause problems such as polymerization, and it can also treat impurities at a fairly high concentration. Even if they have a molecular weight, they can be separated if one of them is an electrolyte.

In the present invention, the impurity to be removed is ionically dissociated and passes through the ion exchange membrane. Therefore, it is related to the dissociation constant of the substance to be removed, but the pH is usually 5 to 10, preferably is 6~
The range is 8.

Furthermore, the temperature when using an ion exchange membrane is not particularly limited, but it is usually preferably in the range of 0 to 50°C, considering the polymerization of (meth)acrylamide and the resistance of the liquid during membrane treatment. .

Furthermore, the concentration of the (meth)acrylamide aqueous solution in the present invention is not particularly limited, and ranges from a concentration of several percent or more in the production of normal (meth)acrylamide to a concentration of 40 to 40%, which can be obtained by concentrating it.
It can be processed up to about 50% by weight.

Furthermore, it is possible to treat impurities contained in the (meth)acrylamide aqueous solution at concentrations ranging from several ppm to several tens of percent.

The device equipped with the ion exchange membrane used in the present invention is one used for concentrating seawater, for example, and does not need to be a special device. in particular,
Acrylonitrile or methacrylonitrile is hydrated using an electrodialysis device consisting of negative and positive electrodes placed at both ends of multiple liquid phase chambers partitioned by alternately arranged anion exchange membranes and cation exchange membranes. The obtained acrylamide or methacrylamide aqueous solution is put into the liquid phase chamber (the liquid phase chamber having the cation exchange membrane on the side facing the cathode) [stock solution side] which has the anion exchange membrane on the side facing the anode of the device, and Ionic substances in the solution are removed by permeating them into the adjacent liquid phase chamber (using distilled water on the permeate side), and as a result, only nonionic substances can remain in the stock solution. Usually, the supply of each liquid to the raw liquid side and the permeate side is performed continuously.

As described above, according to the present invention, unsaturated organic acids, inorganic and organic salts can be removed from an aqueous solution of (meth)acrylamide, which is a nonionic substance. or activated carbon.

Next, the present invention will be explained in more detail with reference to Examples.

Examples Example 1 Acrylamide 19.8% by weight, acrylic acid
An aqueous solution containing 334 ppm and 800 ppm of NaCl was adjusted to pH 7.0 using caustic soda, and the solution was set at a temperature of 25° C. on the stock solution side of an experimental electrodialysis device Du-ob type manufactured by Asahi Glass Co., Ltd. Distilled water was placed on the permeate side of the device and a DC voltage (10 V) was applied while circulating it through the device at a rate of 48/hr each. Approximately 5
The analytical values of the stock solution after hours were 18.7% by weight of acrylamide, 39.3ppm of acrylic acid, and 35ppm of NaCl.
No polymers were detected.

Example 2 Acrylamide 34.0% by weight, acrylic acid
Regarding the aqueous solution containing 632ppm and NaCl1400ppm,
The same operation as in Example 1 was performed. As a result, about 5
The analytical values of the stock solution after hours were 33.9% by weight of acrylamide, 54.6ppm of acrylic acid, and 40ppm of NaCl.
No polymers were detected.

Claims (1)

[Claims] 1 An electrodialysis device consisting of negative and positive electrodes arranged at both ends of a plurality of liquid phase chambers partitioned by alternately arranged anion exchange membranes and cation exchange membranes, with the anion exchange membrane on the side facing the anode. An acrylamide or methacrylamide aqueous solution obtained by hydrating acrylonitrile or methacrylonitrile is placed in a liquid phase chamber, and ionic substances in the solution are permeated into an adjacent liquid phase chamber and removed. A method for purifying an aqueous solution of methacrylamide.